1. Field of the Invention
The present invention relates generally to processor-based devices and, more particularly, to a system and method of automatically switching control of a bus in a processor-based device.
2. Background of the Related Art
This section is intended to introduce the reader to various aspects of art which may be related to various aspects of the present invention which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Currently, many processor-based devices, such as servers, are being designed in smaller, more compact packages. Size restraints are particularly evident in the server market, where data centers having fixed physical space continually require higher computing capacity. Thus, in many data centers, older and larger servers are being replaced with smaller, low profile servers which can increase computing capacity without requiring the center to expand its physical facility. For example, current designs of low profile servers (e.g., 1U servers), which have a reduced height between the base and top of the chassis (e.g., less than 1.75 inches), may replace older, higher profile servers which are stacked vertically in a rack system at a ratio of three low profile servers for every older server (e.g., a 3U server). Provided each server is adequately cooled, the servers may be stacked, such that the replacement ratio of low profile servers to older servers may be maximized.
The reduced height of the low profile chassis for the servers and the compact packaging may create problems with providing adequate airflow to cool the components within the chassis sufficiently. Thus, physical designs of low profile servers are concerned with provision of adequate heatsinking and placement of components to ensure unobstructed airflow paths.
Exemplary components which often present an obstacle to airflow include cables used to interconnect components (e.g., hard drives) to a chassis-mounted printed circuit board (e.g., the motherboard) or to interconnect multiple boards. For example, the motherboard may include expansion connectors which allow additional boards, such as peripheral controller cards, SCSI controller cards, and so forth, to be added to the server. If such interconnecting cables obstruct airflow, then the heated air can recirculate inside the chassis and, consequently, can cause overheating of certain components or even the entire system.
The use of cables within the chassis may be difficult to eliminate altogether, particularly for server designs which provide for versatility in the choice of components that may be used or added. For example, although the motherboard of the server typically may include a SCSI controller for controlling the SCSI device (e.g., hard drives) connected to the SCSI controller, many end-users may desire incorporation of alternate SCSI controller cards which provide different or additional features. Use of alternate SCSI controller cards also may enable the user to ensure uniformity among all servers the user may have, regardless of the system manufacturer. Such a SCSI controller card may be connected to one or more SCSI devices via a SCSI adapter cable having one end connected to the controller card and the other end connected to the SCSI devices. When using a SCSI adapter, the existing connection between the motherboard and the SCSI devices must be decoupled. Placement of a SCSI cable in the server chassis, however, may obstruct airflow due to the low profile of the chassis and the unpredictability of the positioning of the cable, especially after an installation or a service event.
To avoid the complications associated with such a SCSI cable, it would be desirable to maintain the physical connection between the motherboard and the SCSI devices and connect the new SCSI controller card to the motherboard via an expansion port. Either a direct connection or a relatively fixed-position cable could be provided to make the connection between the motherboard and the SCSI controller card. However, such an arrangement introduces other complications, including provision of appropriate signal termination of electrical transmission line ends on the SCSI bus on the motherboard that are present due to the provision of alternate electrical signal paths to different controllers. Appropriate termination may be needed to prevent signal degradation due to signal reflections from the bus ends. Moreover, it would be desirable to provide a feature by which the server, including components on the motherboard, can be made aware of which SCSI controller (e.g., the on-board controller or the expansion controller) has control of the SCSI bus.
The present invention may be directed to one or more of the problems set forth above.